King under the Mountain

At Erebor, Thrór and his people re-established the Kingdom under the Mountain and were very prosperous. Gaining the friendship of the Northmen who lived along the river Celduin. These people later founded the town of Dale and had much trade of goods, beautiful trinkets, and weapons with the Dwarves. The Dwarves of Erebor also had much traffic of ores with their kinsman in the Iron Hills. And the region had peace and prosperity for many years.

In 2770 though their prosperity ended. The Dragon Smaug heard of the wealth of Thrór and his people. And he came south from the Ered Mithrin and sacked the Lonely Mountain, killing many Dwarves. But from the destruction many escaped last of them being Thrór and his son Thráin from the hidden Side Door. So with a small company of kin and faithful followers they made the great wandering south, until they reached the hills of Dunland.

Dunland, and the journey to Moria

In Dunland, his people tried to make a living, but twenty years after the Sack of Erebor despondent and homeless, Thrór left his people and went north with a single companion, Nár, but not before giving his son Thráin II his Ring of Power, along with the map and key to the Lonely Mountain. Thrór wished to see the fabled city of his ancestors, Khazad-dûm.

Eventally they made it over the Redhorn Pass down into Azanulbizar the Dimrill Dale. And when Thrór came to the East-gate of Moria he found it open. Nár begged him to beware, but he took no heed of him, and walked through the gates as the heir who had returned. But he did not come back.

Death

Nár stayed nearby for many days in hiding until he saw Thrór's body flung down the steps; his head was severed and lay face downward on the ground. As he knelt there, Nar saw branded across his forehead in Dwarvish runes the name AZOG.

The Orc then threw a small purse of silver coins at him, calling him a beggar. Nár fled weeping as he went down the Silverlode, while Orcs emerged and began hacking Thrór's body into pieces and throwing them to the crows.

Aftermath

When Nár told Thráin what had happened, he declared war on the Orcs and called all the Seven Houses together for vengeance.
Nine years later at the Battle of Azanulbizar, the climax of the War of the Dwarves and Orcs the death of Thrór was avenged, and Thráin took Azog's severed head, shoved the purse of coins into his mouth and then set it on a stake.